Former Missouri Department of Conservation employees Rochelle Renken and Michael Huffman were on a six-day backpacking trip in Wrangell-St. Elias National Park in Alaska when they disappeared. The experienced hikers were traveling in a rugged and remote area of the park, the National Park Service said. Courtesy National Park Service

Former Missouri Department of Conservation employees Rochelle Renken and Michael Huffman were on a six-day backpacking trip in Wrangell-St. Elias National Park in Alaska when they disappeared. The experienced hikers were traveling in a rugged and remote area of the park, the National Park Service said. Courtesy National Park Service

It is America's largest national park with 13.2 million acres — the same size as Yellowstone National Park, Yosemite National Park and Switzerland combined, boasts the park's website.

The two conservationists were experienced backpackers. Renken had visited Alaska several times and knew how to cross Alaskan rivers, parks officials said in announcing that Renken and Huffman were swept away while trying to cross the Sanford River, a "powerful, glacial river," near the top of the Sanford Glacier.

"Our hearts go out to their family," Steigerwald told the Alaskan newspaper.

The route they had planned to follow through the park, according to the Columbia Missourian, is known as the “Volcanic Traverse,” a 15-mile hike with no trails that is rated "difficult" on the park service website.

To see the spectacular scenery, “either you go up the glacier and over, or you cross the stream,” Steigerwald told the Missourian.

Or, she told the newspaper, you turn back.

In a series of press releases beginning June 29, the park service chronicled the search for the hikers.

Park officials said the two planned to hike from the river, across the Dadina Plateau and end up at the Dadina River, where an air taxi would pick them up June 27. But they weren't there for the pickup, and they had missed two scheduled satellite phone calls to the air taxi operator.

When they missed the plane, the pilot searched from the air for several hours, then reported them "overdue" to park officials who began an intensive air and ground search June 28, according to a National Park Service release.

By Thursday night, the search involved 27 National Park Service employees on the ground and in the air, and five aircraft, including an Alaska State Troopers spotter plane, according to the park service. Ground crews searched along the hikers' proposed route.

After river levels dropped Friday and Saturday, searchers found two gear-filled backpacks in dry river channels with Renken and Huffman's identification in them, and other gear that led them to concentrate around the Sanford River.

They also found footprints along the river, where it emerges from the glacier, that suggested two people preparing for a river crossing, according to a park service release.

Searchers found gear along a seven-mile stretch of the river near where the two had been dropped off June 22. The air and ground search continued into Saturday, but by then searchers found no additional signs of the two, according to the park service.

The ground search had to be scaled back Saturday afternoon because of weather, but the park pilot continued to fly over the area.